LED Upgrades

Recently I looked at an old 3-LED VistaLite rear light and thought
about chucking it and buying one of the new VistaLite Super Nebulas, a
5-LED light which is supposedly even brighter than their previous
5-LED light (the one with the silver plastic reflector behind the
LEDs).

Modified VistaLite: the 60° LED is in the middle

But I decided to try to upgrade the LEDs on it instead. The circuit
board is easy to get at, you just remove a couple of screws and you
can flip it over to look at the backside. Looking closely at the
circuit board, I found that the power tracks were parallel and the
LEDs straddled it, and there were holes for 5 LEDs!

I went to Maplin
and bought some Hyperbright and Extreme brightness
LEDs. The Hyperbright ones had a 30° viewing angle and light
output of 3.5 candles, and the Extreme brightness ones an 8°
viewing angle and light output of 7 candles.

Installing the new LEDs was easy. Both the LEDs I took out and the new
ones had a flat edge, so I put the new ones in so the flat edge was
the same place as flat edge of the old ones.

The Hyperbright ones were both brighter and had a wider viewing angle
than the ones that were in it before. A definite win. I installed one
Extreme brightness LED, but it had such a narrow viewing angle that
most of the time it weren't contributing anything to the light output.
So I removed it.

Still curious, I went back to Maplin, wanting to try out their 60°
(1.5 candle) Hyperbright LEDs. I bought a few, but was a bit
disturbed to find out that they had three legs and a completely round
top. The shop guy said that they were basically two LED devices stuck
into one clear plastic package. The Maplin catalog says that the LEDs
share a common cathode (not that that means much to me) so there were
three legs, not four.

The longer middle leg of the 60° LED (top) corresponds with the
longer leg of the 30° LED (bottom).

So I had to figure out how to install three legs into two holes. I
guessed that the longer leg on the three-leg LED (the shared leg of
the two devices, which was the middle leg) corresponded with the
longer leg on the normal LEDs. So I soldered the two outside legs of
the 60° LED together and cut one of them off. I soldered the LED into
the circuit board with the remaining side leg attached to the place
I'd put the flat parts of the normal LED, and the longer middle leg on
the other side.

(The Maplin catalog says that the 60° LEDs have a common cathode,
and they also say that the cathode is the part marked with a short
lead and the flat spot on a normal LED . However, the shared leg of
the 60° LEDs was definitely the middle leg, and it was longer, and it
clearly corresponded with the longer lead on the normal LED. So
they've got something wrong there! At any rate, the positive voltage
needs to be applied to the longer legs and the negative voltage to the
shorter legs for both the normal and wide-angle LEDs I got.)

I held the modified
VistaLite about 1" from the wall to see the beam pattern.

And it worked! I found out that the LED is 60°s in one direction
only: it puts out a beam that's much wider than it is tall. This is
what you'd expect from two LEDs side by side, and it's perfect for LED
rear lights, since you need more side-to-side visibility than up-down
visibility. The plastic bit of the LED is wider in one dimension than
the other, so you can figure out how to install it so the wideness of
the beam is oriented in the right direction.

Although the 60° LED has a lower brightness (candlepower) than
the 30° LEDs, its much wider viewing angle increases
dramatically the angle at which you can see the VistaLite, making it a
clear win.

Looking directly at VistaLite (left), the 60° LED looks more or less
like the others. Looking at the VistaLite from the side (right) shows
that the middle LED clearly improves the side viewing angle!

Happy with my results on the old VistaLite, I went to butcher the
other ones (I have quite a collection of VistaLite rear lights!). The
cicuit board of the newer lights makes it even easier to figure out
how to put in the new LEDs, as there's a circle with a flat edge
printed on the curcuit board. I discovered that the LEDs used in the
5-LED lights that include the silvery plastic reflector are identical
to the 30° Hyperbright ones, so it wasn't any use replacing
those. Still, it was worth taking one or two of them out and putting
in 60° ones instead to improve the viewing angle.

This went along fine until I came to the last VistaLite I had. I
opened this one up to find that its LEDs looked like they were
soldered in backwards! The flat spot on the LED was opposite the flat
spot printed on the circuit board. So what was happening here? Were
the voltages flipped around on this circuit board, or did it have
strange LEDs, with the flat spots on the opposite side? I didn't want
to experiment with my last 60° LED, so I used one of the too-narrow
Extreme brightness ones. I first put it in so its flat spot lined up
with the flat spots of the other LEDs. It didn't work. I then took it
out and reversed it, so the flat spot lined up with the flat spot
printed on the circuit board. And then it worked. Which meant that the
voltages of the circuit board were normal, it's just that the LEDs
installed in it had the flat spots opposite the place they normally
were. So I then installed the 60° LED the way I had in the other
VistaLites, with the side leg soldered next to the flat spot on the
diagram and the longer middle leg soldered on the opposite
side. Success. I think the moral of this story is, if the circuit
board has any printed diagrams, put the longer leg opposite the
printed flat spot.

I took a look at a Cateye LD500 I had around to see if I could upgrade
that, but the circuit board seems solidly soldered into place, so I
gave up.

If you feel like upgrading your VistaLites (or any other LED light
where you can easily get at the back of the circuit board) the Maplin
part numbers are:

CH22Y for the 60° Hyperbright ones with 3 legs
UK20W for the 30° Hyperbright ones with 2 legs